* Dollar index falls to near 8-month low

* Euro hits 8-month high, Italy still seen a major risk

* Aussie soars after RBA holds rates

By Anirban Nag

LONDON, Oct 1 (Reuters) - The dollar fell to a 1-1/2 year low against the safe-haven Swiss franc and a near eight-month low against a basket of currencies on Tuesday as the first U.S. government shutdown in 17 years spooked markets.

Expectations the shutdown will hurt the economy and prompt the Federal Reserve to postpone withdrawal of monetary stimulus weighed on the U.S. currency.

The selloff gathered pace in European trade with the dollar index falling to 79.864, its lowest since Feb. 13, and down 0.4 percent on the day.

The dollar's weakness lifted the euro to an eight-month high of $1.3589. The single currency was also helped by the prospect of Italian Prime Minister Enrico Letta's coalition government surviving a confidence vote on Wednesday.

The Swiss franc hit a 1-1/2 year high of 0.89925 francs per dollar on trading platform EBS.

Speculation the U.S. shutdown could prompt an early release of the closely watched monthly U.S. jobs report added to market uncertainty..

Reflecting the nervousness, near-term implied volatilities, a gauge of how choppy a currency is likely to be, rose. The one-month euro/dollar implied volatility rose to 7.5 percent, from around 6.6 percent on Friday.

"We do not know how long this impasse in the U.S. will last. If it persists, there is a chance it will hurt economic growth and affect chances of Fed tapering - all of which is dollar negative," said Daragh Maher, strategist, at HSBC.

"In the short term, it's better to avoid the dollar."

A potentially bigger political battle looms over raising the U.S. government's borrowing authority. Failure to do so by mid-October could result in a historic U.S. default.

The dollar also lost 0.3 percent to 97.835 yen, moving back toward a one-month low of 97.50 yen hit on Monday, according to EBS data.

The dollar's weakness offered some reprieve to the yen, which has been under pressure, with the Japanese government on track to raise the national sales tax to 8 percent in April from 5 percent.

To soften the tax's impact, Prime Minister Shinzo Abe will unveil on Tuesday an economic stimulus package worth 5 trillion yen or more, according to a final draft seen by Reuters.

Some are not convinced the economy can absorb the tax hike and are expecting more easing from the Bank of Japan.

"There are concerns whether the economy is robust enough to cope and our suspicion is that the decision increases the pressure to ease monetary policy further," Tom Levinson, strategist at ING wrote in a note.